Support for a workshop on the pathogenesis of murine retroviral infection of the central nervous system is requested. Approximately one third of AIDS patients develop neurologic disease caused by the retrovirus HIV infection of the brain. The other human retroviruses also appear to infect and affect the human central nervous system. The pathogenesis of neurologic diseases associated with human retroviral infection is unclear. While there are several animal models available that mimic HIV encephalitis, many of these (e.g. SIV encephalitis and Visna) are expensive and time consuming to work with. Given the primitive state of our knowledge regarding the pathogenesis of retroviral mediated neurologic disease, having and inexpensive model in the murine system would greatly facilitate rapid and efficient testing of pathogenesis hypotheses. Approximately twenty years ago a neurotropic ecotropic murine leukemia virus was isolated from paralyzed feral mice. In the intervening years numerous models using a variety of mouse strains, in addition to molecular cloning of the virus, have led to greater understanding of how the central nervous system is perturbed during retroviral infection. Nevertheless, with the proliferation of models and development temperature sensitive mutants of Moloney murine leukemia virus, there has been a profusion of theories regarding retroviral mediated neurologic disease. Much of the basic data regarding this disease (such as the nervous system cells infected) are subject to intense controversy. It is the purpose of the proposed workshop to bring together all of the research groups currently active in the field to share data and positions on these important models. By examining the various model systems it is the intention of the workshop to air the controversies and direct experimentation at resolving differences. An additional goal of the conference will be to produce a published work that summarizes the models and controversial issues. Better awareness of these important systems by investigators not specifically in the field may engender new interest in this relatively inexpensive model for studying neurologic diseases caused by retroviruses.